* Full disclosure, my Auditor is currently on sale, therefore one may understandably be led to think my reference to it is purely out of vested interest. However, I hope this review will offer an honest representation of my graduation experience from one generation to the other, while acknowledging the positive traits of an amplifier that has long remained under the shadow of its newer siblings.

** A version of this article is presented in Greek at Audiohub.gr

After my successful coexistence with the excellent Auditor from the German company SPL, I was given the opportunity to upgrade my office system with the newer Phonitor X, a preamplifier and headphone amplifier that has established itself in recent years as a reference point for many well-known hobbyists in the field. In fact, the upgrade from Auditor to Phonitor X is nothing less than an upgrade from the first generation of Phonitor to the second, as the Auditor was just a minimalist version of that amplifier without the proprietary crossfeed circuit (Phonitor Matrix) SPL is quite renowned for.

Too much has already been written over the various Phonitor models, so I won’t be repeating what’s already very extensively covered by others. The Auditor is a different case however; indeed, very little information is available online and you need to dig all the way to 2012 in order to get a first glimpse of a discussion. That being said, many people understandably graduated from the Auditor to the Phonitor X, keeping their faith to the many good traits SPL has consistently offered its ‘Pro-fi’ series over the years.

The differences between the Auditor and the Phonitor X have to do both with the evolution of the proprietary 120V rail op-amp circuit that SPL has developed for the analogue stage of its products, as well as the change of the output impedance of the headphone connectors: the Auditor was rated at 9Ω, therefore best suited for mid-to-high impedance headphones, while the Phonitor X is rated at 0.18Ω for the single-ended output / 0.36 for the balanced, widening therefore its base to cover for low impedance headphones such as those at the nowadays popular 32Ω category. Being a Phonitor means that is also features SPL’s Matrix crossfeed circuit, as well as two very catchy VU-meters that evoke a very Nagra-like 'professional' aesthetic.

Old and new: The Auditor strongly resembles other products that SPL has developed for the studio, while the Phonitor X stands as a regular consumer product with its own distinct aesthetic (namely, prosumer, or, in SPL’s terminology, “Pro-fi”).



VU-meters in mute mode: an extremely useful feature as many Phonitors are known to have blown their circuit because their owners plugged their headphones on a 'live' signal!



The Phonitor X does anything but lag behind other headphone amplifiers famously renowned for their power capacity such as the Schiit Mjolnir, the Burson Soloist / Conductor, or the Auralic Taurus. The following measurements are featured in the manual, without specifying differences between unbalanced and balanced output:

Max. Output Power (at +30 dBu @ 1 kHz)
1 W x 2 @ 600 Ohm impedance
2 W x 2 @ 300 Ohm impedance
3.7 W x 2 @ 120 Ohm impedance
2.9 W x 2 @ 47 Ohm impedance
2.7 W x 2 @ 32 Ohm impedance

On the contrary, SPL’s website features measurements that differ quite evidently from the aforementioned values, showing an emphasis on headphones with medium to high impedance:

Unbalanced Max. Output Power
2.7W x 2 @ 600 Ohm
5W x 2 @ 300 Ohm
1W x 2 @ 32 Ohm

Balanced Max. Output Power
8W x 2 @ 600 Ohm
3.5W x 2 @ 300 Ohm
0.7 x 2 @ 32 Ohm

In view of these differences, as well as the confusion that arises with some measurements mentioned in an older review of the Phonitor XE at The Headphoneer, I contacted SPL who clarified that the reason is due to a silent improvement they made to the circuit in order to add protection against short circuits. As the company states that they reserve their right to such updates without prior notice, along with the fact that very few people got in touch with them over the subject, they felt they should let both measurements roll without further clarification unless specifically asked by an interested party. That being said, it looks like Phonitors that were put in circulation over the last 3-4 years and henceforth output in accordance to the measurements specified on SPL’s website.

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[Update: 21 Oct 2021] According to user @aleniola76 who contacted SPL on the same subject (see here), the company responded that

(...) both [measurements] are correct. The first one is the maximum output power when a +30dBu input 1k sine wave is send into the device. The second one is the output power when sending a 1k sine wave into the device causing a THD of 1%. The newer documents will show the later because it is better suited to get a feeling of how much power you will get out of the device until the sound get's less enjoyable. Keep in mind we are talking about a 1k sine signal. So even this value is not a real life value but that's the downside of all these specs – in the end they are just numbers to make devices comparable but do not say anything about the sound. I have never listened to headphones which could not be driven by a Phonitor before – so I assume it's enough power to drive them all.

Click to expand...

To my understanding, the measurements on SPL's website represent their best case scenario —and the one most akin to real life circumstances.

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Despite the ample power that covers for the majority of various headphone models, the Phonitor X has three stages of gain at the signal level. With the exception of notable beasts that are known to draw unnaturally large amounts of power to be driven properly, I honestly cannot imagine where it may be needed given the amount of power already available on tap:

DIP switch 1: ON = The headphone output is boosted to +22 dB.
DIP switch 2: ON = The headphone output is boosted to +12 dB.
DIP switch 1 and 2: ON = If both DIP switches 1 and 2 are ON, a boost of +24 dB is applied.

In comparison, the Auditor has much less power, but has more than enough stock when it comes to the high-impedance headphones that it is designed for (call me Beyerdynamic, Sennheiser, AKG, etc.):

Unbalanced Max. Output Power
1.7 W (+32.2 dBm) @ 1 kHz and 600 Ohm connection
360 mW (+25.6 dBm) @ 1 kHz and 30 Ohm connection

Both the Phonitor and the Auditor benefit from SPL's proprietary design of the main amplifier circuit (120 Voltair technology), which offers an incredible capacity for really large voltage peaks combined with an exemplary low noise floor. This is something that originally impressed me with the Auditor, as it gave the amplifier its capacity for fatigue-free listening even at high volumes, albeit in a very subtle and discreet manner. On the contrary, the remarkable nominal power of the Phonitor X gives it terrific analytical skills and lets it dissect the signal it receives into its most minute details.

Here’s where the similarities between the two models end. The Phonitor X clearly shows that it is the superior amplifier, taking the effortless neutral sound of the first generation and launching it into the stratosphere. The Auditor is very easy on the ear, and I would even venture to claim it’s rather forgiving, proposing thus a more relaxed version of SPL’s signature neutrality that might be more suited to headphones like the HD600, complementing its drawbacks rather than revealing them in their naked truth. In the end, the Auditor will take advantage of the 120V rail technology’s voltage headroom to create the impression of effortlessness. On the opposite side, the Phonitor X develops from the same trait to offer a very vocal silence: its dead quiet noise floor, combined with its vast power reserves, creates the impression of a void that’s hard not to acknowledge its presence. This is not your typical studio-grade neutral. Oddly but emphatically, the Phonitor X is present by removing itself out of the equation with admirable dexterity in an unusually refined manner. In my honest opinion, SPL has hit the jackpot with its proprietary op-amp design; certainly a treat to the seasoned ear that strays from seeking for an attention - grabbing signature.

Instead of getting more technical, I will just refer to the two videos SPL uses to explain its technology and substantiate its advantages.





In the current range of SPL, one can find a version of the Phonitor in many flavours and for equally many wallets:

• around 1K € there’s the Phonitor SE (which is the cheapest option available in the line-up ) a stripped-down version that only features the amplifier stage and one single-ended output
• at 1,4K € you can find the Phonitor E as an end-of-life product, featuring one single-ended and one balanced output (along with the advantages of the extended power capacity available through the latter)
• Finally, at € 2-2.5K, you have Phonitor X and the Phonitor XE, the former having an additional pre-amplification circuit while the latter serves purely as a headphone amplifier offering as many outputs as possible for this purpose (1 x single-ended, 1 x 4pin balanced, 2 x 3pin balanced at the back)

For me, the choice of Phonitor X also brought an unexpected added value as an active preamplifier, driving my Fostex PM-04d desktop monitors with remarkable control and agility, at the same time revealing them for a capacity to scale that I couldn’t have imagined from such a middle of the line product. Admittedly I also didn’t imagine the advantages that active pre-amplification could bring to the table: the Auditor already offered a kind of pass-through signal output through 2xXLR, leaving the job of driving to the amplifier circuit of the monitors which I thought adequate, to say the least. However, the improvement I got from active driving was so great that I almost feel the need to complain about the poor standalone job the Fostex are doing in this regard!



Thus I close my impressions from this remarkable amplifier. As the days go by it becomes more and more clear that the Phonitor is not an amplifier that will mask the weaknesses of the gear you put behind it, probably putting me in a position to sell both the HD600 and the HiFiMan x Massdrop Model XX that I have in my roster. Therefore, while the first impressions are undoubtedly positive, the Phonitor's ability to mercilessly reveal mistakes is something that under certain conditions puts its owner in a rather uncomfortable position. In comparison, the Auditor is much friendlier, keeping most of the positive traits of the SPL warm-neutral house sound without offending the other components in the signal chain.

It is evident from the very first auditions that the Phonitor X can certainly keep its promise to act as a safe reference point for many critical auditions to come, guiding my future explorations with other components steadily and reliably. Judging from the experience I accumulated over the years through my ATCs (see signature), I also find it certain that at the end of this journey, once the mix is right, the Phonitor X may compensate for its revealing character with a performance that only other, more sophisticated implementations with special character can bring one to cross over (I’m thinking Susvara combined with Acoustic Masterpiece AM201-H or Trafomatic Primavera here). However, as a reference sound, I am already convinced that the Phonitor X sets a benchmark that can hardly be challenged at any degree...

The background

Meze Audio is a Romanian company that has long been well-known in the Head-Fi circles through its affordable and widely used on-ear closed headphones 99 Classics and their variants, which were later followed by the equally accessible 11 Neo and 12 Classics IEMs. In recent years, Meze has shaken the waters with their €3,000 open-backed orthodynamic Empyrean, followed by their €1000 hybrid IEM Rai Penta. As these lines were being written, Meze also introduced their entry-level Rai Solo, which is a more accessible version of this new IEM series price-wise at €250 featuring their own take on a dynamic driver using proprietary technology.

This review unit came to my hands through the European leg of the Meze Rai Penta World Tour, organised by @MezeTeam and @Andykong. Being the second reviewer in line, the Penta had already been broken in with at least 50 hours of listening. The packaging was sleek but also relatively simple for a €1000 IEM, and included headphones, a single-ended 20 litz four-strand silver-plated copper cable with MMCX terminals, a fairly extensive set of tips and a hard zippered case. Inside the case were also an airplane adapter and a 6.3mm adapter. Meze also offers 2.5mm and 4.4mm balanced cables, however they need to be purchased separately as they are not included in the standard package. Fortunately the organiser made sure we had both of these cables at our disposal.



The IEM

Aesthetically, the Rai Penta is a small, CNC-shaped solid aluminium piece of jewellery, anodised in a satin blue petrol colour that I can only compare to something like the iPhone 11 Pro in its Midnight Green version. Both looks and touch give the Penta body a luxurious feel, while the combination of robustness and small size reminds me strongly of the RHA CL1's ceramic housings. The same also applies to the silver plated copper cable in a transparent shell, which achieves an exceptional combination of suppleness, weight and flexibility, without ever being microphonic. The name 'Penta' reflects the handset's setup using five driver units on each side, one dynamic and two BAs in pairs (2X2) customised by Meze. Meze gives great attention to controlling the airflow inside the Penta’s housing by using tubes of different length carved into the body of the chamber, combined with their twin ports which aim to balance the pressure inside the units with the body of air trapped inside the ear canal.

(Source: Meze Audio)

Both of these approaches are very interesting in their own respect: the first looks to take advantage of the inert aluminium body in order to better control the resonances inside the chamber, while the second gives the drivers more breathing space by working synergistically with the ear canal, which I found to result in a very welcome relief of the pressure that is usually accumulated on my eardrum. The body of the Penta is itself very well designed from an anatomical point of view, and sits very comfortably on the ear concha with minimal effort. Meze has also managed to fit the five driver units into a very convenient size that sits flush to the ear while hardly creates any sort of nuisance, thus allowing for long hours of listening sessions and yes, sleeping over them with very little pressure accumulating on the ear, albeit they will be felt eventually after some time because of their robust aluminium body (that is, if you’re sleeping on your side for the better part of the night).


(Source: Meze Audio)

The nozzle is typical for a universal IEM and under certain conditions I found it long enough to provide a somewhat deep insertion, albeit still within universal IEM limitations and obviously nothing quite like what Etymotic does with their own IEMS. One interesting point here is that the thick stem tends to push most ear tips towards the back of the nozzle, resulting in a very shallow fit and therefore, a quite open baffle. I found this to be beneficial to my understanding of the Penta’s timbre, and my impressions are mostly based on this assumption. In any case, Meze provides the owner of the Penta with four pairs soft silicone tips (XS, S, M, L), one pair of double-flange tips, and one pair of foam tips.As for myself, I ended up using my last-gen Spiral Dots ++ which I found to give a more open sense of air, and a most welcome openness to the mid and lower high frequencies without messing greatly with the bottom end or the general signature of the Penta. On the other hand, I was unable to form impressions with cable rolling as I didn’t have suitable cables available in my inventory.

The sound


For the purpose of this review of the Meze Rai Penta, the following units were recruited

1. On the IEM side, the RHA CL1 and T20i, the Ultimate Ears 900s, the FLC8s and the Etymotic Hf3 (later cross-checked with my Etymotic ER4s)
2. On the sources side, the Chord Mojo, the FiiO X5iii and the FiiO BTR3, as well as the Questyle QP2R, and the Questyle CMA400i desktop DAC/amp which has a special IEM output.
3. For reference tonality, the Sennheiser HD600, AKG K240DF, and Sennheiser HD800 with SDR and AnaxII mod (i.e., all of the original tuning minus the notorious 6kHz peak and subsequent ringing), played mainly by SPL Auditor and for the minor part from Questyle 400i.

After the first few tests I ended up using mostly the Questyle QP2R, which seemed to fit the character of Rai Penta by bringing to the table a rugged body combined with very good technical ability. In contrast, the Mojo gave the Penta a solid foundation to its character but without giving it this extra gravitas that the Penta seem to benefit so greatly from (I’m not talking bass boost here, rather some better authority on the lower registers). Pairing with the FiiO BTR3 bluetooth receiver/DAC/portable amp was also interesting, as it proved to be a capable match highlighting both the FiiO’s tendency towards a sparkling airy sound and the Penta’s efficiency with lower powered devices. This same character of the BTR3 was evident also on the FiiO X5iii, albeit this time the AKM traits of airy and spacious mids were conveyed with much better confidence. That being said, I didn’t find the Penta completely transparent to their sources; instead I found them mostly to retain their own character with minor but discernible changes to the critical ear. I also found the same to be true while changing from single-ended to balanced: the latter managed to pin down everything in place with a more solid rendering of the scene, however I didn’t find the differences to be night-and-day. That said, it should be noted that due to the Penta’s sensitivity (110dB SPL / 1mW, with a maximum input power of 30mW) both the Questyle units gave an audible hiss which I chose to disregard in order to maintain the benefits of the pairing. Should the background were pitch-black, the differences between single-ended and balanced might have been more pronounced. For the same reason, I was unable to listen to the Penta through the SPL Auditor via the 6mm adapter.



Having said that, the first impression Penta gave me was that of a full-bodied handset, with a focus on low frequencies and mild (even relatively rolled-off) highs. Starting from the quite impressive yet very natural rumble at the lowest registers (if available on the track) the Penta cross over smoothly to the lower midrange without any noticeable bleeding, as well as without overwhelming any frequency from there up. The highs sound very natural, with a mesmerising smoothness that is perhaps costing in soundstage and air between the instruments. The soundstage appears deep rather than expansive, with good layering and good articulation, without reaping laurels in terms of technicalities or of precision on the placement of instruments in space.

Based on the FR measurements found on several sites, the Rai Penta ultimately appear to have a smoothed over "U" character, with more pronounced bass up to 100 Hz, a smooth midrange dip at 400-500 Hz and a generous midrange boost up to 2kHz. The mild rise in the treble gives the Penta some air but it remains very smooth, therefore some may find themselves needing more some sparkle in the upper registers. It’s worth noting that the boost in the sub and lower registers that gives the Penta their quasi-visceral sensation doesn’t seem to overload the eardrum with pressure —such as I’ve often noticed with IEMs with similar characteristics such as the FLC8s or the CL1— which might have to do with Meze’s ‘Pressure Equalization System’. This results in the Rai Penta’s incredible capacity to sustain long listening sessions —and by “long”, in my case, I’m referring to 6-7 hours sessions with little to indiscernible fatigue.


(Source: crinacle.com, antdroid.net)

Based on sound signature alone, the Meze Rai Penta can quickly become extremely addictive. They performed with great confidence on all the test tracks of Dr Chesky's Ultimate Headphone Demonstration disk, while in the church organ track of Dr Chesky's Sensational, Fantastic, and Simply Amazing Binaural Sound Show they were able to show once again how well they fare with the lowest registers of the audible spectrum, especially concerning performances with analog instruments or live recordings.
This was quite evident with the O-zone Percussion Group's "Jazz Variants" on Manger's demo album, where Penta delivered percussion with superb naturalness, convincing attack and decay, capable texture and sufficient clarity.



Equally striking was the Penta’s exuberance with Brahms' abysmal Ein Deutsches Requiem by the Swedish Radio Symphony Orchestra under the direction of Daniel Harding (Harmonia Mundi), where they managed to perform while maintaining a homogeneous ‘organic’ sense of character for the larger part of the spectrum, as well as a capable articulation that managed to hide a certain weakness in speed and transitions.

Finally, Penta played just as convincingly in Lana del Rey's latest Norman ****ing Rockwell,
as well as in Airelle Besson's very charming jazz fusion album Radio One, Oliver Nelson's classic jazz album The Blues and the Abstract Truth, and a tribute by Qobuz to the great, and the recently deceased, Jessye Norman.
Meze claims that the Rai Penta were designed for “a balanced sound signature with impeccable micro-detailing provides unrivalled realism all across the wide frequency range, from 4Hz to 45 kHz”, a claim that doesn’t stray far from being true.

Nonetheless, comparing with headphones that have a flatter response revealed some restraint in the midrange, which for some may be a concern. For example, Diana Krall's well-known grainy voice in The Girl in the Other Room seemed a bit pushed to the background, remaining embedded within the overall organic atmosphere that Penta conveyed to the scene,

while in Hiromi's Duet with Chick Corea I found that the usually crystalline notes of the middle and high octaves of the pianos were rather overshadowed by the resonance of the pianos’ bodies.

This observation led me to return to some of the songs I had listened to earlier with a more critical ear, which revealed that despite their organic nature the Penta seemed to be lacking in the technical capability that some other headphones of the 1K tier may be more well-versed in, while the luscious mids may indeed be overshadowing the smoothed out higher frequencies of the Penta.



Conclusion

In the end, the Penta's greatest asset seems to be their capacity to maintain an overall homogeneity of its character and good articulation throughout the full range of their 4 Hz to 45 kHz claimed spectrum. The former easily leads to the feeling that it is a mild and lush set of IEMs that can easily help someone to hours of fatigue-free listening, and the latter seems to hide some tonal imperfections that keep the Penta from being a reference tuning. Personally, I could easily imagine them as part of a collection that covers for someone’s critical auditions with other IEMs. In this respect, I can easily imagine the Penta as a daily driver that allows you to get lost in the music as you would get lost in your thoughts on your way to work or immersed in a book. On the other hand, those who are looking to the Rai Penta for critical listening and a ‘reference’ tuning may find it lacking. However, even so, the Rai Penta can be persuading simply by having you listen to the music. This may very well be the reason why they cover a spot on several reference lists in magazines and reviewers’ sites worldwide.



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For this review I have to thank Andy Kong for offering access to the Meze Rai Penta, as well as John Demou at Aurion Audio, Greece, for lending me the Questyle CMA400i and Questyle QP2R. Aurion Audio is also the official importer of Meze for Greece. I'm not affiliated with Meze, Andy Kong, or Aurion Audio in any way other than the opportunity and support they gave me for this review. The Meze Rai Penta sample unit stayed with me for 10 days and is now on its way to continue the European part of the World Tour. All pics featured in this review are my own, courtesy of Audiohub.gr, unless otherwise noted. For a Greek version of this review see here.